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| Titel |
The viability of prescribed fire for mitigating the soil degradational impacts of wildfire |
| VerfasserIn |
R. A. Shakesby, C. P. M. Bento, C. S. S. Ferreira, A. J. D. Ferreira, C. R. Stoof, E. Urbanek, R. P. D. Walsh |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062834
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| Zusammenfassung |
| Prescribed (controlled) fire has become an important strategy primarily to limit the likelihood
of more devastating wildfire. The considerable increase in wildfire activity in recent decades
throughout the Mediterranean, and in Portugal in particular, has meant that this strategy has
become increasingly popular despite inherent fears of people about fire of any sort. Despite
many studies of the impact of wildfire on soil erosion and degradation, relatively little
research has assessed impacts of prescribed fire on soil in Portugal or elsewhere in the
Mediterranean. As part of the DESIRE research programme, this paper addresses this
research gap by investigating hillslope-scale losses of soil, soil organic matter and selected
nutrients before and after an experimental fire (representing a ‘worst case-scenario’
prescribed fire) in a shrub-vegetated catchment in central Portugal. Comparison is provided
by post-fire monitoring of a nearby hillslope affected by a wildfire of moderate
severity. Hillslope-scale measurements were carried out over c. 3 years using sediment
fences with contributing areas of up to c. 0.5 ha. Eroded sediment was periodically
removed from the fences both before and after the fire at intervals ranging from a
few weeks to several months depending on rainfall characteristics and logistics.
Erosion expressed as g/m2 and g/m2/mm of rainfall was determined. Figures for
long-term (c. 10 years) erosion under unburnt conditions for this vegetation type were
obtained from a small bounded plot and from sediment accumulating in a weir pool
draining a sub-catchment within the prescribed-fire catchment. In addition, soil organic
matter and selected nutrients, including K2O, P2O5 and Total N, were measured
in the eroded sediment and in the pre-burn and post-burn in situ soil. The results
indicate that both the wildfire and prescribed fire caused erosion that was orders of
magnitude higher than for long-term plot-scale and hillslope-scale erosion recorded
under unburnt conditions. Total post-fire erosion measured over 21 -2 years was
relatively high for this worst case scenario prescribed fire even when compared
with published results from smaller-scale plots monitored after wildfire elsewhere
in the Mediterranean, which would be expected to be higher. Nevertheless, the
post-fire hillslope-scale losses appear to have had a relatively low impact on the thin,
stony, degraded soils. This is thought also to be the case following the wildfire, even
though it caused somewhat higher erosion. Its other serious effects (damage to
habitat and property, loss of life), however, mean that wildfire can never be viewed as
acceptable, particularly where people live in close proximity to highly fire-prone
terrain. The results support the viability of prescribed fire as a strategy for combating
wildfire on shrub-vegetated terrain in this wet Mediterranean environment. This
view of a low impact of prescribed fire on the terrain may be different where the
stability of the soil is reduced by disturbance through ploughing, where soils are very
thin or contain relatively few stones, or where fire is carried out too frequently. |
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